Ever since I moved into a different apartment, the internal air was really humid (69-72% humidity), so I ran a big dehumidifier to try to get it down. I also got two digital hygrometers.
What happened then was rather odd: The humidity barely budged down at all - staying at 62-65% most of the time regardless - but then my eyes and airway+lungs got quite dry and irritated. I figured it might be the airflow drying out the eyes, but even then, the internal air was always still at 62-65% humidity - occasionally even going back up to 70% or beyond again - which I had thought ought to be damp enough that it couldn’t cause eye or lung dryness. It got to the point where the skin on one of my finger knuckles cracked open and started bleeding, which usually doesn’t happen unless I’m in a really dry place for a very long time.
How wet can the air be and still cause dryness at the same time?
Excessively moist air can cause an imbalance in that film, and while it won’t actually dry your eyes out, it can cause irritation that will mimic the symptoms of dry eyes. Excessively dry or moist air can do that.
Here is a page from an eye group in Atlanta:
Humidity levels in the air can directly impact your tear film, which is essential for keeping your eyes moist and comfortable. Dry environments, such as air-conditioned rooms or cold weather, can cause tears to evaporate more quickly, exacerbating dry eye symptoms. Excess moisture in the air may also lead to an imbalance in the tear film, potentially increasing irritation for some individuals. High humidity can also worsen underlying conditions like allergies, contributing to eye discomfort.
High humidity can irritate the lungs for sure. I lived on Guam for a couple of years and had really bad asthma as a youth, and the humid air really did a number on me. (Guam’s humidity levels will vary between 66%-84%, and are worst at night.) Much the same way that eyes can experience problems with humid air, your lungs can absolutely be irritated by it. I had a nagging cough for over a year and sometimes a tickle that felt like I was dried out.
It could also be that it’s not nearly as humid as your meter suggests, per Beck’s suggestion.
Dry eyes have a lot of causes, from autoimmune disorders like Sjögren’s syndrome, use of fans, relative dehydration, tear duct problems, eye surgery, Meibomian gland dysfunction, inflammation, infrequent blinking, and contact lens irritation.
If you live in a hot spot drink more water, ease off on fans and/or consider using cheap artificial tears, Visine or clean water to rinse your peepers? Allergies tend to cause watery eyes but I suppose after the deluge things are dryer…